Animated Solution for Chemistry - Organic Chemistry: The major product of the following reaction is

The oxidation of alkyl and acyl benzenes is a classic and high-yield concept in organic chemistry. When faced with a strong oxidizing agent like alkaline potassium permanganate ($KMn{O}_4$), the side chains of a benzene ring undergo dramatic transformations. Let's dive into the mechanism and understand exactly how $p$-methylacetophenone is converted into its final product.

We start with $p$-methylacetophenone, a benzene ring adorned with two distinct side chains at the para positions: a methyl group ($-C{H}_3$) and an acetyl group ($-COC{H}_3$).

The reagent provided is alkaline $KMn{O}_4$ accompanied by heat. This is a notoriously vigorous oxidizing agent. Its primary target? Any carbon atom directly attached to the benzene ring, provided it has at least one benzylic hydrogen.

When $KMn{O}_4$ attacks the methyl group, it oxidizes the carbon entirely, stripping away the hydrogens and replacing them with oxygen to form a carboxylate ion ($-CO{O}^{-}$). This is a standard benzylic oxidation.

But what about the acetyl group? You might wonder if it resists oxidation since it's already partially oxidized. However, under these harsh conditions, acyl groups also succumb to oxidative cleavage. The bond between the carbonyl carbon and the adjacent methyl group is broken, and the carbonyl carbon is fully oxidized to a carboxylate ion.

Because the reaction occurs in an alkaline medium ($KOH$), the intermediate formed is a potassium salt: potassium terephthalate.

The second step of the reaction involves the addition of dilute sulfuric acid ($H_{2}S{O}_4$). This is a simple acidification step. The $H^{+}$ ions from the acid protonate the carboxylate ions ($-CO{O}^{-}$), converting them into stable carboxylic acid groups ($-COOH$).

The final product is a benzene ring with two carboxylic acid groups at the para positions, known as terephthalic acid (or benzene-1,4-dicarboxylic acid). This elegant transformation highlights the sheer power of $KMn{O}_4$ in standardizing various side chains into uniform carboxylic acid groups.